1. Field of the Invention
The present invention relates to a medium judgment method, a computer-readable storage medium and a medium judgment program which determine whether it is a storage medium with which unauthorized duplication of original storage medium is performed, in order to prevent the unauthorized duplication, and also relates to an optical disk drive which uses the medium judgment method.
2. Description of the Related Art
Conventionally, the contents of software, such as application programs, still pictures, and moving pictures, in many cases are distributed in the form of CD-ROM or in compliance with the same. Moreover, various rewritable CDs (CD-R, CD-RW, etc.) are used for the distribution media carrying the contents of software. Furthermore, recently, a hybrid CD having the read-only area and the rewritable area has been developed as a new distribution medium. It is proposed to distribute a hybrid CD which substitutes for CD-ROM, and in the hybrid CD the contents of software are beforehand written in the read-only area of the hybrid CD.
A description will be given of the data structure of CD-R or CD-RW. In the following, CD-R or CD-RW will be called the disk. The information area is provided to hold information on the disk, and it is composed of a lead-in area, a data area, and a lead-out area.
The starting-position information indicating the starting position of two or more subsequent tracks on the disk is written in the lead-in area. This information is also called TOC (table of contents) information. The data (the contents of software) is written in the data area. The lead-out area is provided to indicate a position of the end of the data area on the disk.
The R-information area is disposed inside the information area. This R-information area is provided for the PCA or RMA, and it is the area that is specific to CD-R and CD-RW. The PCA is the area for calibrating the recording laser power, and the RMA is the area for recording management information.
On the substrate of the disk, the wobbling groove and the land prepit are formed. The wobbling groove is the data-carrying groove which is waved with a certain amplitude and spatial frequency, and it is provided to generate a gate signal for detecting the land prepit etc. The wobble signal, which is described in the optical disk by the wobbling of the track, is indicative of the absolute-time information called ATIP (absolute time in pre-groove).
The land prepit is an isolated pit which is disposed in accordance with a certain rule on the area called the land between adjacent grooves, and it is used for high precision positioning at the time of data recording, etc.
Several medium judgment methods have been proposed in order to take advantage of the above-described characteristics of the disk, and prevent that the contents of software recorded in the original medium are not illegally copied to other media.
As the conventional method for prevention of illegal copying, there is a method in which the contents of software are encrypted using the specific information that is specific to each disk and recorded on the disk, and the encrypted data is recorded on the disk. When reproducing the data from the disk, the encrypted contents are decrypted using the specific information. Refer to Japanese Laid-Open Patent Application No. 2000-100068.
Japanese Laid-Open Patent Application No. 2002-182770 discloses a method in which, using the information which is given to the authorized disk and which is not rewritable, it is determined whether the information on a disk of interest for medium judgment is in agreement with the information on the authorized disk. In the disclosure of Japanese Laid-Open Patent Application No. 2002-182770, the example of DVD-ROM is taught.
There is another method in which the ID of an optical disk drive of an authorized user is recorded on an optical disk, and the ID read from the optical disk is compared with the ID of a currently used optical disk drive. If the agreement occurs, the starting of the program recorded on the optical disk is allowed for the currently used optical disk drive. Refer to Japanese Laid-Open Patent Application No. 2000-123479.
There is still another method in which the disk and the reproduction permission medium (for example, an IC card) are set in the reproducing apparatus, and the reproduction management information of the disk and the reproduction permission information of the IC card are read out, and the checking of these data is performed. If the match occurs, the reproduction of the contents of software is allowed. Refer to Japanese Laid-Open Patent Application No. 11-167769.
However, according to the conventional illegal copy prevention methods, it is necessary to use a special optical disk drive that is in compliance with a corresponding one of the illegal copy prevention methods when reproducing the contents of software from the disk. Furthermore, the ATIP (absolute time in pre-groove) is specific to the rewritable optical disks, such as CD-R and CD-RW, and the ATIP does not exist on the read-only optical disks, such as CD-ROM. Therefore, the read-only disk drive, such as a CD-ROM drive, is not capable of reading out the ATIP from the disk when a rewritable optical disk with the ATIP recorded is inserted into the read-only disk drive.